This invention relates to sampling systems, and more particularly to apparatus for drawing representative samples of free-flowing powder, granular, or flake type material as it flows through an angular or vertical gravity spout.
In most conveying or dispensing systems particulate material is not spread uniformly throughout the cross-sectional area of the conveying or dispensing tube, such that there often tends to be a concentration of the particulate material at one side of the tube. Where the particulate material comprises a mixture of two or more substances with different characteristics, the substances may be collected together at one side or another in the tube, rather than being spread uniformly across the tube. As a result, it is not possible to simply insert a probe into the conveying tube and extract a sample, since such procedure will not provide a truly representative sample. Also, dust problems often arise in the systems because of the exceedingly small size of particles conveyed, resulting in further complications for sampling apparatus.
Sampling apparatus, such as that disclosed in Clements, U.S. Pat. No. 4,120,203, is available for connection to the pipe of a pneumatic conveying system for drawing representative samples of the material, as it flows through the conveying pipe. Such constructions typically move a sample collecting head, having an elongated sample receiving slot, across the particulate stream from one side of the stream to the other. In applications for gravity systems extensive rail assemblies must be disposed adjacent the sealed housing containing the sample collecting head, for accommodating movement of the collecting head from one side of the particulate stream to the other within such housing. That is, the overall size of such sampling apparatus has been determined primarily by the mechanism for moving the collecting head through its collecting cycle. In addition to taking up too much space, conventional sampler apparatus also can be vulnerable to dust problems, because of the greater number of components utilized. There is presently available no sampler apparatus capable of withdrawing a representative sample from a conveying or dispensing system while occupying a minimum of space in such system.